The feeding of ruminants (bovine animals, sheep, goats, and other animals of the suborder Ruminantia) presents special problems and special opportunities. Special opportunities arise from the ability of ruminants to utilize insoluble cellulosic fiber which can be broken down by certain microorganisms but is generally not digestible by monogastric mammals such as pigs. The special problems arise from the tendency of certain feeds to inhibit digestion of fiber in the rumen and from the tendency of the rumen to limit the utilization of some of the components of certain feeds such as fat and protein.
Traditional feeds have not been able to meet the energy demands of ruminants, especially dairy cattle. This prevents dairy cattle from maximizing their potential in terms of milk production. The most common approach to increasing the energy density of the bovine diet is to increase the proportion of grain at the expense of forage. However, excessive grain in the diet has been shown to be associated with metabolic disorders which have a negative impact on the productive and reproductive performance of the animal, which in turn has been associated with a marked reduction in the life span of dairy cows.
An alternative way to increase the energy intake of ruminants is to increase their intake of triglycerides having saturated and unsaturated fatty acid residues (sometimes collectively referred to as "fats"; the unsaturated fats are sometimes referred to as "oils"). Fats can be an excellent source of energy for ruminants, but too much fat in the rumen can disrupt some of the highly complex ruminant digestion processes. For example, fat can coat fiber in the feed, thereby decreasing digestion of cellulose in the rumen. Fats can be toxic to microorganisms in the rumen and can decrease cation availability.
Wellons, U.S. Pat. No. 4,919,940, proposed an increase in the proportion of saturated fatty acid residues in triglycerides mixed with the dry matter of ruminant feeds, because saturated fats have less harmful effects in the rumen than unsaturated fats. But apparently, the saturated fat content of cattle feed can have an effect upon the degree of saturation of milk fat. Since the effect of saturated fats on sterol levels in humans is a matter of some concern, there may be drawbacks inherent in Wellons' approach to the formulation of feeds.
Palmquist, U.S. Pat. No. 4,642,317, proposes supplying fatty acids from tallow, for example, to ruminants in the form of their calcium salts. However, Palmquist expresses reservations about the use of high levels of calcium salts of unsaturated fatty acids (such as the calcium salt of linolenic acid), because unsaturated triglycerides are said to cause milk fat to turn rancid very quickly.
Another proposal involves "protecting" fats with a coating or encapsulation or some similar temporary barrier to digestion typically comprising protein treated with an aldehyde such as formaldehyde. The "protected" unsaturated fats pass through the rumen without being digested and without being hydrogenated and are absorbed further on in the digestive tract of the ruminant. Typically, safflower oil or ground soybeans and sunflower seeds are enclosed or encapsulated in formaldehyde-treated casein or the like and fed to dairy cattle. The formaldehyde-treated protein resists breakdown in the rumen but is hydrolyzed in the acidic environment of the abomasum. The triglycerides in the safflower oil or ground soybeans or ground sunflower seeds bypass the rumen and are digested further on in the digestive tract, thereby providing an energy source for the cattle without disrupting fermentation processes in the rumen.
While ruminants derive energy solely from feeds, they derive their protein needs from a combination of microbial protein (derived from microbes present in the rumen) and feed protein that escapes digestion (bypasses) the rumen. Since there is a limit to microbial protein synthesis, bypass protein required increases as milk production increases. It is now common practice to include a source of bypass protein in the diet of lactating dairy cows. Inclusion of such protein sources as well as an energy source is essential for these animals to achieve their genetic potential for milk production.
There are many commercial forms of bypass fat and protein on the market. Most of the commercially available bypass fats are in one of the "protected" forms. Some of the protein content of cattle feed is obtained as a by-product of vegetable oil manufacturing processes. The meal (crushed seeds) left over after the vegetable oil has been removed is high in protein and low in triglyceride content.
A need exits for a method for increasing the energy content of the diet of ruminants, especially dairy cattle, that is relatively simple to use but (1) does not adversely affect digestion in the rumen and (2) does not increase the amount of saturated fatty acid in the milk.